Various auxiliary braking devices have been proposed (See Patent Literature 1 and Patent Literature 2, for example).
Patent Literature 1 and Patent Literature 2 are both constructed such that the auxiliary braking device is not operated during an operation of an accelerator pedal (See FIG. 5).
Therefore, according to such auxiliary braking device, if the accelerator pedal is pressed while the auxiliary braking device is operating, a vehicle stops braking and changes to an acceleration state instantly from a deceleration state, and a shock occurs in the vehicle.
In the vehicle provided with the auxiliary braking device with such constructions, repetition of acceleration/deceleration increases, a frequency of coasting decreases and a fuel consumption of the vehicle deteriorates on a flat road when an inter-vehicle distance to a preceding vehicle frequently increases/decreases while following the preceding vehicle or on a road in mountains with continuous ups and downs.
Since acceleration/deceleration increase, shifting up and shifting will be repeated in a vehicle provided with an automatic transmission, which might give a sense of discomfort to a driver.